1. Field of the Invention
The present invention relates to a scroll compressor. More specifically, the present invention relates to a scroll compressor having enhanced lubrication by the employment of one or both of a vent arrangement and oil retention features that facilitate oil delivery at compressor start-up and during compressor operation.
2. Description of the Background Art
Scroll compressors typically comprise two basic scroll members each with scroll wraps that interleave to create a series of compression chambers therebetween. Relative movement between the scroll members cyclically recreates such compression chambers at the outer periphery of the scroll members where suction gas enters thereinto. Those chambers close and decrease in volume as the relative orbital motion of the scroll members continues compressing gas therein. Upon reaching the center of the scroll members, the compressed gas is discharged for use.
Lubricant is typically supplied to various scroll compressor components, including an anti-rotation mechanism, bearings and other compressor parts. Such lubricant is typically conveyed from a sump in the lower portion of the compressor through the compressor's drive shaft which drives at least one of the scroll members. Rotation of the drive shaft, which often includes an inclined oil gallery and/or an oil pump, causes lubricant to be drawn from the sump and delivered to the top of the drive shaft and thereafter to locations where lubricant is needed.
In scroll compressors having vertical drive shafts, much of the oil which moves upward through the oil gallery in the drive shaft exits the shaft through a discharge opening at the upper end of the shaft. That opening is typically located below a central region of the end plate of one of the scroll members.
The central region of a scroll member is typically hot due to the compression of gas that occurs at that location. In scroll compressors used in refrigeration systems, the oil conveyed upward through the drive shaft can contain entrained liquid refrigerant or refrigerant in the gaseous form. If in the liquid form, refrigerant conveyed upward through the drive shaft may vaporize in the vicinity of the lubricant opening above the drive shaft due to the heat in that location. Such vaporization or the conveyance of refrigerant gas into this area through the oil gallery can displace oil in a location where it is needed and/or otherwise adversely affect compressor lubrication. For instance, the existence of too much vaporized refrigerant in this area can create a backpressure which operates against and reduces the flow of oil attempting to move upward through the drive shaft.
In attempts to address these problems and/or other concerns, some compressors include a vent or vent-like system. Representative examples of such compressors and/or systems are disclosed in U.S. Pat. Nos. 4,792,296; 4,875,840; 4,877,381; 4,997,349; 5,176,506; 5,533,875; 5,885,066 and 6,102,160. A common drawback of these systems is that the limited radial length of the various vent lines associated with such systems fail to take full advantage of centrifugal force that might otherwise be available to assist in lubricant flow.
Another problem related to the lubricant needs of scroll compressors at compressor start-up relates to the amount of time it may take for oil to make its way to various compressor systems that require lubrication. If the amount of time it takes for such lubricant to reach such surfaces is too great, relatively dry bearing surfaces may be damaged before they become properly lubricated. To address this problem, some compressors have a stand pipe or reservoir installed near the upper end of the shaft. The reservoir can hold a small charge of oil that is stored adjacent and can be delivered to bearing surfaces at compressor start-up. Examples of such compressors and arrangements are found in U.S. Pat. Nos. 4,403,927; 4,575,320; 4,666,381 and 6,012,911. Although such systems may be effective, they can require additional parts or offer additional complexity that may increase a compressor's reliability and/or increase its cost.